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Upgrade of the ALICE Experiment: Letter Of Intent
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2014 J. Phys. G: Nucl. Part. Phys. 41 087001
ALICE-UG-001 CERN-LHCC-2012-012 / LHCC-I-022 September 8, 2012
Upgrade of the ALICE Experiment
Letter Of Intent
0.1 The ALICE Collaboration
B. Abelev71, J. Adam37, D. Adamov´a78, A.M. Adare129, M.M. Aggarwal82, G. Aglieri Rinella33, M. Agnello102 ,88, A.G. Agocs128, A. Agostinelli27, Z. Ahammed124, N. Ahmad17, A. Ahmad Masoodi17, S.A. Ahn64, S.U. Ahn40 ,64, I. Aimo22, M. Ajaz15, A. Akindinov50, D. Aleksandrov94, B. Alessandro102, A. Alici98 ,12, A. Alkin3, E. Almar´az Avi˜na60, J. Alme35, T. Alt39, V. Altini31, S. Altinpinar18, I. Altsybeev125, C. Andrei74, A. Andronic91, V. Anguelov87, J. Anielski58, C. Anson19, T. Antiˇci´c92, F. Antinori99,
P. Antonioli98, L. Aphecetche108, H. Appelsh¨auser56, N. Arbor67, S. Arcelli27, A. Arend56, N. Armesto16, R. Arnaldi102, T. Aronsson129, I.C. Arsene91, M. Arslandok56, A. Asryan125, A. Augustinus33, R. Averbeck91, T.C. Awes79, J. ¨Ayst¨o42, M.D. Azmi17 ,84, M. Bach39, A. Badal`a105, Y.W. Baek66 ,40, R. Bailhache56, R. Bala85 ,102, R. Baldini Ferroli12, A. Baldisseri14, F. Baltasar Dos Santos Pedrosa33, J. B´an51, R.C. Baral52, R. Barbera26, F. Barile31, G.G. Barnaf¨oldi128, L.S. Barnby96, V. Barret66, J. Bartke112, M. Basile27, N. Bastid66, S. Basu124, B. Bathen58, G. Batigne108, M. Battistin33, B. Batyunya62, J. Baudot61,
C. Baumann56, R. Bavontaweepanya109, I.G. Bearden76, H. Beck56, N.K. Behera44, I. Belikov61, F. Bellini27, R. Bellwied118, E. Belmont-Moreno60, G. Bencedi128, S. Beole22, I. Berceanu74, A. Bercuci74,
Y. Berdnikov80, D. Berenyi128, M. Berger111, A.A.E. Bergognon108, D. Berzano22 ,102, L. Betev33, A. Bhasin85, A.K. Bhati82, J. Bhom122, L. Bianchi22, N. Bianchi68, J. Bielˇc´ık37, J. Bielˇc´ıkov´a78,
A. Bilandzic76, S. Bjelogrlic49, F. Blanco118, F. Blanco10, D. Blau94, C. Blume56, M. Boccioli33, S. B¨ottger55, A. Bogdanov72, H. Bøggild76, M. Bogolyubsky47, L. Boldizs´ar128, M. Bombara38, J. Book56, H. Borel14, A. Borissov127, F. Boss´u84, C. Bortolin33, J.A. Botelho Direito33, M. Botje77, E. Botta22, E. Braidot70, P. Braun-Munzinger91, M. Bregant108, T. Breitner55, T.A. Broker56, T.A. Browning89, M. Broz36, R. Brun33, E. Bruna22 ,102, G.E. Bruno31, D. Budnikov93, H. Buesching56, S. Bufalino22 ,102, P. Buncic33, O. Busch87, Z. Buthelezi84, D. Caballero Orduna129, D. Caffarri28 ,99, X. Cai7, H. Caines129, E. Calvo Villar97, P. Camerini24, V. Canoa Roman11, G. Cara Romeo98, W. Carena33, F. Carena33, N. Carlin Filho115, F. Carminati33, A. Casanova D´ıaz68, J. Castillo Castellanos14, J.F. Castillo Hernandez91, E.A.R. Casula23, V. Catanescu74, T. Caudron33, C. Cavicchioli33, C. Ceballos Sanchez9, J. Cepila37, P. Cerello102, B. Chang42 ,131, N. Chankhunthot109, S. Chapeland33, J.L. Charvet14, S. Chattopadhyay95,
S. Chattopadhyay124, I. Chawla82, M. Cherney81, C. Cheshkov33 ,117, B. Cheynis117, V. Chibante Barroso33, D.D. Chinellato118, P. Chochula33, M. Chojnacki76 ,49, S. Choudhury124, P. Christakoglou77,
C.H. Christensen76, P. Christiansen32, T. Chujo122, S.U. Chung90, C. Cicalo101, L. Cifarelli27 ,33 ,12, F. Cindolo98, J. Cleymans84, F. Coccetti12, F. Colamaria31, D. Colella31, A. Collu23, G. Conesa Balbastre67, Z. Conesa del Valle33, M.E. Connors129, G. Contin24, J.G. Contreras11, T.M. Cormier127,
Y. Corrales Morales22, P. Cortese30, I. Cort´es Maldonado2, M.R. Cosentino70, F. Costa33, M.E. Cotallo10, E. Crescio11, P. Crochet66, E. Cruz Alaniz60, R. Cruz Albino11, E. Cuautle59, L. Cunqueiro68, A. Dainese28 ,99, H.H. Dalsgaard76, A. Danu54, E. Da Riva33, I. Das46, D. Das95, S. Das4, K. Das95, A. Dash116, S. Dash44, S. De124, G.O.V. de Barros115, A. De Caro29 ,12, G. de Cataldo104, C. Decosse33, J. de Cuveland39, A. De Falco23, D. De Gruttola29, H. Delagrange108, A. Deloff73, N. De Marco102, E. D´enes128, S. De Pasquale29, A. Deppman115, G. D Erasmo31, R. de Rooij49, M.A. Diaz Corchero10, D. Di Bari31, T. Dietel58, C. Di Giglio31, S. Di Liberto100, A. Di Mauro33, P. Di Nezza68, R. Divi`a33, Ø. Djuvsland18, A. Dobrin127 ,32, T. Dobrowolski73, B. D¨onigus91, O. Dordic21, O. Driga108, A.K. Dubey124, A. Dubla49, L. Ducroux117, W. Dulinski61, P. Dupieux66, A.K. Dutta Majumdar95, D. Elia104,
D. Emschermann58, H. Engel55, B. Erazmus33 ,108, H.A. Erdal35, B. Espagnon46, M. Estienne108, S. Esumi122, D. Evans96, G. Eyyubova21, L. Fabbietti111, D. Fabris28 ,99, J. Faivre67, D. Falchieri27, A. Fantoni68, M. Fasel91 ,87, R. Fearick84, D. Fehlker18, L. Feldkamp58, D. Felea54, A. Feliciello102, B. Fenton-Olsen70, G. Feofilov125, J. Ferencei37, A. Fern´andez T´ellez2, A. Ferretti22, A. Festanti28, J. Figiel112,
M.A.S. Figueredo115, S. Filchagin93, D. Finogeev48, F.M. Fionda31, E.M. Fiore31, E. Floratos83, M. Floris33, S. Foertsch84, P. Foka91, S. Fokin94, E. Fragiacomo103, A. Francescon33 ,28, U. Frankenfeld91, U. Fuchs33, C. Furget67, M. Fusco Girard29, J.J. Gaardhøje76, M. Gagliardi22, A. Gago97, M. Gallio22,
D.R. Gangadharan19, P. Ganoti79, C. Garabatos91, E. Garcia-Solis13, C. Gargiulo33, I. Garishvili71, P. Gasik111, J. Gerhard39, M. Germain108, C. Geuna14, M. Gheata54 ,33, A. Gheata33, B. Ghidini31, P. Ghosh124, P. Gianotti68, M.R. Girard126, P. Giubellino33, E. Gladysz-Dziadus112, P. Gl¨assel87, M. Goffe61, R. Gomez114 ,11, M. Gomez Marzoa33, E.G. Ferreiro16, L.H. Gonz´alez-Trueba60, P. Gonz´alez-Zamora10, S. Gorbunov39, A. Goswami86, S. Gotovac110, L.K. Graczykowski126, R. Grajcarek87, A. Grelli49, C. Grigoras33, A. Grigoras33, V. Grigoriev72, A. Grigoryan1, S. Grigoryan62, B. Grinyov3, N. Grion103, P. Gros32, J.F. Grosse-Oetringhaus33, J.-Y. Grossiord117, R. Grosso33, F. Guber48, R. Guernane67, B. Guerzoni27, M. Guilbaud117, K. Gulbrandsen76, H. Gulkanyan1, T. Gunji121, A. Gupta85, R. Gupta85, R. Haake58, Ø. Haaland18, C. Hadjidakis46, M. Haiduc54, H. Hamagaki121, G. Hamar128, B.H. Han20,
L.D. Hanratty96, A. Hansen76, Z. Harmanov´a-T´othov´a38, J.W. Harris129, M. Hartig56, A. Harton13, D. Hatzifotiadou98, S. Hayashi121, A. Hayrapetyan33 ,1, S.T. Heckel56, M. Heide58, H. Helstrup35, A. Herghelegiu74, G. Herrera Corral11, N. Herrmann87, B.A. Hess123, K.F. Hetland35, B. Hicks129, H. Hillemanns33, B. Hippolyte61, A. Hoenle111, Y. Hori121, P. Hristov33, I. Hˇrivn´aˇcov´a46, C. Hu61, M. Huang18, T.J. Humanic19, D.S. Hwang20, R. Ichou66, S. Igolkin33, P. Ijzermans33, R. Ilkaev93, I. Ilkiv73, M. Inaba122, E. Incani23, P.G. Innocenti33, G.M. Innocenti22, M. Ippolitov94, M. Irfan17, C. Ivan91, V. Ivanov80, A. Ivanov125, M. Ivanov91, O. Ivanytskyi3, A. Jachołkowski26, P. M. Jacobs70, H.J. Jang64, M.A. Janik126, R. Janik36, P.H.S.Y. Jayarathna118, S. Jena44, D.M. Jha127, R.T. Jimenez Bustamante59, P.G. Jones96, H. Jung40, A. Junique33, A. Jusko96, A.B. Kaidalov50, S. Kalcher39, P. Kaliˇn´ak51, T. Kalliokoski42, A. Kalweit57 ,33, J.H. Kang131, V. Kaplin72, A. Karasu Uysal33 ,130 ,65, O. Karavichev48, T. Karavicheva48, E. Karpechev48, A. Kazantsev94, U. Kebschull55, R. Keidel132, B. Ketzer111, P. Khan95, S.A. Khan124, M.M. Khan17, K. H. Khan15, A. Khanzadeev80, Y. Kharlov47, B. Kileng35, B. Kim131, J.S. Kim40, J.H. Kim20, D.J. Kim42, D.W. Kim40 ,64, T. Kim131, S. Kim20, M.Kim40, M. Kim131, S. Kirsch39, I. Kisel39, S. Kiselev50, A. Kisiel126, J.L. Klay6, J. Klein87, C. Klein-B¨osing58, M. Kliemant56, A. Kluge33, M.L. Knichel91, A.G. Knospe113, M.K. K¨ohler91, C. Kobdaj109, T. Kollegger39, A. Kolojvari125,
M. Kompaniets125, V. Kondratiev125, N. Kondratyeva72, A. Konevskikh48, V. Kovalenko125, M. Kowalski112, S. Kox67, G. Koyithatta Meethaleveedu44, J. Kral42, I. Kr´alik51, F. Kramer56, A. Kravˇc´akov´a38,
T. Krawutschke87 ,34, M. Krelina37, M. Kretz39, M. Krivda96 ,51, F. Krizek42, M. Krus37, E. Kryshen80, M. Krzewicki91, Y. Kucheriaev94, T. Kugathasan33, C. Kuhn61, P.G. Kuijer77, I. Kulakov56, J. Kumar44, P. Kurashvili73, A. Kurepin48, A.B. Kurepin48, A. Kuryakin93, S. Kushpil78, V. Kushpil78, H. Kvaerno21, M.J. Kweon87, Y. Kwon131, P. Ladr´on de Guevara59, I. Lakomov46, R. Langoy18, S.L. La Pointe49, C. Lara55, A. Lardeux108, P. La Rocca26, R. Lea24, M. Lechman33, K.S. Lee40, S.C. Lee40, G.R. Lee96, I. Legrand33, J. Lehnert56, R. Lemmon106, M. Lenhardt91, V. Lenti104, H. Le´on60, I. Le´on Monz´on114, H. Le´on Vargas56, Y. Lesenechal33, P. L´evai128, S. Li7, J. Lien18, R. Lietava96, S. Lindal21, V. Lindenstruth39, C. Lippmann91 ,33, M.A. Lisa19, H.M. Ljunggren32, P.I. Loenne18, V.R. Loggins127, V. Loginov72, D. Lohner87, C. Loizides70, K.K. Loo42, X. Lopez66, E. L´opez Torres9, G. Løvhøiden21, X.-G. Lu87, P. Luettig56, M. Lunardon28, J. Luo7, G. Luparello49, C. Luzzi33, R. Ma129, K. Ma7, D.M. Madagodahettige-Don118, A. Maevskaya48,
M. Mager57 ,33, D.P. Mahapatra52, A. Maire87, M. Malaev80, I. Maldonado Cervantes59, L. Malinina62 ,,ii, D. Mal’Kevich50, P. Malzacher91, A. Mamonov93, L. Manceau102, L. Mangotra85, V. Manko94, F. Manso66, C. Mansuy33, V. Manzari104, Y. Mao7, A. Mapelli33, M. Marchisone66 ,22, J. Mareˇs53, G.V. Margagliotti24 ,103, A. Margotti98, A. Mar´ın91, C. Markert113, M. Marquard56, D. Marras23, I. Martashvili120, N.A. Martin91, P. Martinengo33, M.I. Mart´ınez2, A. Mart´ınez Davalos60, G. Mart´ınez Garc´ıa108, Y. Martynov3, A. Mas108, S. Masciocchi91, M. Masera22, A. Masoni101, L. Massacrier108, A. Mastroserio31, A. Matyja112 ,108, C. Mayer112, J. Mazer120, G. Mazza22, M.A. Mazzoni100, F. Meddi25, A. Menchaca-Rocha60, J. Mercado P´erez87, M. Meres36, Y. Miake122, L. Milano22, J. Milosevic21 ,,iii, A. Mischke49, A.N. Mishra86 ,45, D. Mi´skowiec91, C. Mitu54, S. Mizuno122, J. Mlynarz127, B. Mohanty124 ,75, L. Molnar128 ,33 ,61, L. Monta˜no Zetina11, M. Monteno102, E. Montes10, T. Moon131, M. Morando28, D.A. Moreira De Godoy115, S. Moretto28, A. Morreale42, A. Morsch33, V. Muccifora68, E. Mudnic110, S. Muhuri124, M. Mukherjee124, H. M¨uller33, M.G. Munhoz115, S. Murray84, L. Musa33, J. Musinsky51, A. Musso102, B.K. Nandi44, R. Nania98, E. Nappi104, C. Nattrass120, T.K. Nayak124, S. Nazarenko93, A. Nedosekin50, M. Nicassio31 ,91, M.Niculescu54 ,33, B.S. Nielsen76, T. Niida122, S. Nikolaev94, V. Nikolic92, S. Nikulin94, V. Nikulin80, B.S. Nilsen81, M.S. Nilsson21, F. Noferini98 ,12, P. Nomokonov62, G. Nooren49, N. Novitzky42, A. Nyanin94, A. Nyatha44, C. Nygaard76, J. Nystrand18, A. Ochirov125, H. Oeschler57 ,33, S. Oh129, S.K. Oh40, J. Oleniacz126, A.C. Oliveira Da Silva115, C. Oppedisano102, A. Ortiz Velasquez32 ,59, A. Oskarsson32, P. Ostrowski126, J. Otwinowski91, K. Oyama87, K. Ozawa121, Y. Pachmayer87, M. Pachr37, F. Padilla22, P. Pagano29, G. Pai´c59, F. Painke39, C. Pajares16, S.K. Pal124, A. Palaha96, A. Palmeri105, V. Papikyan1, G.S. Pappalardo105, W.J. Park91, A. Passfeld58, B. Pastirˇc´ak51, C. Pastore104, D.I. Patalakha47, V. Paticchio104, B. Paul95, A. Pavlinov127, T. Pawlak126, T. Peitzmann49, H. Pereira Da Costa14,
E. Pereira De Oliveira Filho115, D. Peresunko94, C.E. P´erez Lara77, D. Perini33, D. Perrino31, W. Peryt126, A. Pesci98, V. Peskov33 ,59, Y. Pestov5, P. Petagna33, V. Petr´aˇcek37, M. Petran37, M. Petris74, P. Petrov96, M. Petrovici74, C. Petta26, S. Piano103, M. Pikna36, P. Pillot108, O. Pinazza33, L. Pinsky118, N. Pitz56, D.B. Piyarathna118, M. Planinic92, M. Płosko´n70, J. Pluta126, T. Pocheptsov62, S. Pochybova128, P.L.M. Podesta-Lerma114, M.G. Poghosyan33, K. Pol´ak53, B. Polichtchouk47, W. Poonsawat109, A. Pop74, S. Porteboeuf-Houssais66, V. Posp´ıˇsil37, B. Potukuchi85, S.K. Prasad127, R. Preghenella98 ,12, F. Prino102, C.A. Pruneau127, I. Pshenichnov48, G. Puddu23, C. Puggioni23, V. Punin93, M. Putiˇs38, J. Putschke127, E. Quercigh33, H. Qvigstad21, A. Rachevski103, A. Rademakers33, T.S. R¨aih¨a42, J. Rak42,
A. Rakotozafindrabe14, L. Ramello30, A. Ram´ırez Reyes11, R. Raniwala86, S. Raniwala86, S.S. R¨as¨anen42, B.T. Rascanu56, D. Rathee82, K.F. Read120, J.S. Real67, K. Redlich73 ,,iv, R.J. Reed129, A. Rehman18, P. Reichelt56, M. Reicher49, R. Renfordt56, A.R. Reolon68, A. Reshetin48, F. Rettig39, J.-P. Revol33, K. Reygers87, L. Riccati102, R.A. Ricci69, T. Richert32, M. Richter21, P. Riedler33, W. Riegler33, F. Riggi26 ,105, A. Rivetti22, M. Rodr´ıguez Cahuantzi2, A. Rodriguez Manso77, K. Røed18 ,21, D. Rohr39, D. R¨ohrich18, R. Romita91 ,106, F. Ronchetti68, P. Rosnet66, S. Rossegger33, A. Rossi33 ,28, C. Roy61, P. Roy95, A.J. Rubio Montero10, R. Rui24, R. Russo22, E. Ryabinkin94, A. Rybicki112, S. Sadovsky47, K. ˇSafaˇr´ık33, R. Sahoo45, P.K. Sahu52, J. Saini124, H. Sakaguchi43, S. Sakai70, D. Sakata122, A.B. Saleem15, C.A. Salgado16, J. Salzwedel19, S. Sambyal85, V. Samsonov80, X. Sanchez Castro61, L. ˇS´andor51, A. Sandoval60, M. Sano122, G. Santagati26, R. Santoro33 ,12, J. Sarkamo42, E. Scapparone98, F. Scarlassara28, R.P. Scharenberg89, C. Schiaua74, R. Schicker87, C. Schmidt91, H.R. Schmidt123, S. Schuchmann56, J. Schukraft33, T. Schuster129, Y. Schutz33 ,108, K. Schwarz91, K. Schweda91, G. Scioli27, E. Scomparin102, P.A. Scott96, R. Scott120, G. Segato28, I. Selyuzhenkov91, S. Senyukov61, J. Seo90, S. Serci23,
E. Serradilla10 ,60, A. Sevcenco54, A. Shabetai108, G. Shabratova62, R. Shahoyan33, N. Sharma82 ,120, S. Sharma85, S. Rohni85, I. Sgura104, K. Shigaki43, K. Shtejer9, Y. Sibiriak94, E. Sicking58, S. Siddhanta101, T. Siemiarczuk73, D. Silvermyr79, C. Silvestre67, G. Simatovic59 ,92, G. Simonetti33, R. Singaraju124, R. Singh85, S. Singha124 ,75, V. Singhal124, B.C. Sinha124, T. Sinha95, B. Sitar36, M. Sitta30, T.B. Skaali21, K. Skjerdal18, R. Smakal37, N. Smirnov129, R.J.M. Snellings49, W. Snoeys33, C. Søgaard76 ,32, R. Soltz71, H. Son20, J. Song90, M. Song131, C. Soos33, F. Soramel28, I. Sputowska112, M. Spyropoulou-Stassinaki83, B.K. Srivastava89, J. Stachel87, I. Stan54, I. Stan54, G. Stefanek73, M. Steinpreis19, E. Stenlund32, G. Steyn84, J.H. Stiller87, D. Stocco108, M. Stolpovskiy47, P. Strmen36, A.A.P. Suaide115, M.A. Subieta V´asquez22, T. Sugitate43, C. Suire46, R. Sultanov50, M. ˇSumbera78, X. Sun7, T. Susa92, T.J.M. Symons70, A. Szanto de Toledo115, I. Szarka36, A. Szczepankiewicz112 ,33, A. Szostak18, M. Szyma´nski126, J. Takahashi116, J.D. Tapia Takaki46, A. Tarantola Peloni56, A. Tarazona Martinez33, A. Tauro33,
G. Tejeda Mu˜noz2, A. Telesca33, C. Terrevoli31, J. Th¨ader91, D. Thomas49, R. Tieulent117, A.R. Timmins118, D. Tlusty37, C. Tobon Marin33, A. Toia39 ,28 ,99, H. Torii121, L. Toscano102, V. Trubnikov3, D. Truesdale19, W.H. Trzaska42, T. Tsuji121, A. Tumkin93, R. Turchetta107, R. Turrisi99, T.S. Tveter21, J. Ulery56, K. Ullaland18, J. Ulrich63 ,55, A. Uras117, J. Urb´an38, G.M. Urciuoli100, G.L. Usai23, M. Vajzer37 ,78, M. Vala62 ,51, L. Valencia Palomo46, S. Vallero87, J. Van Beelen33, P. Vande Vyvre33, J. Van Hoornen33, M. van Leeuwen49, L. Vannucci69, A. Vargas2, R. Varma44, M. Vasileiou83, A. Vasiliev94, V. Vechernin125, M. Veldhoen49, M. Venaruzzo24, E. Vercellin22, S. Vergara2, R. Vernet8, M. Verweij49, L. Vickovic110, G. Viesti28, J. Viinikainen42, Z. Vilakazi84, O. Villalobos Baillie96, Y. Vinogradov93, A. Vinogradov94, L. Vinogradov125, T. Virgili29, Y.P. Viyogi124, A. Vodopyanov62, S. Voloshin127, K. Voloshin50, G. Volpe33, B. von Haller33, I. Vorobyev125, D. Vranic91, J. Vrl´akov´a38, B. Vulpescu66, A. Vyushin93, B. Wagner18, V. Wagner37, R. Wan7, D. Wang7, Y. Wang7, Y. Wang87, M. Wang7, D. Wang7, K. Watanabe122, M. Weber118, J.P. Wessels33 ,58, U. Westerhoff58, J. Wiechula123, J. Wikne21, M. Wilde58, G. Wilk73, A. Wilk58, M.C.S. Williams98, B. Windelband87, M. Winter61, L. Xaplanteris Karampatsos113, C.G. Yaldo127, Y. Yamaguchi121, H. Yang14 ,49, S. Yang18, P. Yang7, S. Yasnopolskiy94, J. Yi90, Z. Yin7, I.-K. Yoo90, J. Yoon131, W. Yu56, X. Yuan7, I. Yushmanov94, V. Zaccolo76, C. Zach37, C. Zampolli98, S. Zaporozhets62, A. Zarochentsev125, P. Z´avada53, N. Zaviyalov93, H. Zbroszczyk126, P. Zelnicek55, I.S. Zgura54, M. Zhalov80, H. Zhang7, X. Zhang70 ,66 ,7, F. Zhou7, Y. Zhou49, D. Zhou7, H. Zhu7, J. Zhu7, J. Zhu7, X. Zhu7, A. Zichichi27 ,12, A. Zimmermann87, G. Zinovjev3, Y. Zoccarato117, M. Zynovyev3, M. Zyzak56
Affiliation notes
iDeceased
iiAlso at: M.V.Lomonosov Moscow State University, D.V.Skobeltsyn Institute of Nuclear Physics, Moscow, Russia
iiiAlso at: University of Belgrade, Faculty of Physics and ”Vinˇca” Institute of Nuclear Sciences, Belgrade, Serbia
ivAlso at: Institute of Theoretical Physics, University of Wroclaw, Wroclaw, Poland
Collaboration Institutes
1A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation, Yerevan, Armenia 2Benem´erita Universidad Aut´onoma de Puebla, Puebla, Mexico
4Bose Institute, Department of Physics and Centre for Astroparticle Physics and Space Science (CAPSS), Kolkata, India
5Budker Institute for Nuclear Physics, Novosibirsk, Russia
6California Polytechnic State University, San Luis Obispo, California, United States 7Central China Normal University, Wuhan, China
8Centre de Calcul de l’IN2P3, Villeurbanne, France
9Centro de Aplicaciones Tecnol´ogicas y Desarrollo Nuclear (CEADEN), Havana, Cuba
10Centro de Investigaciones Energ´eticas Medioambientales y Tecnol´ogicas (CIEMAT), Madrid, Spain 11Centro de Investigaci´on y de Estudios Avanzados (CINVESTAV), Mexico City and M´erida, Mexico 12Centro Fermi - Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, Rome, Italy 13Chicago State University, Chicago, United States
14Commissariat `a l’Energie Atomique, IRFU, Saclay, France
15COMSATS Institute of Information Technology (CIIT), Islamabad, Pakistan
16Departamento de F´ısica de Part´ıculas and IGFAE, Universidad de Santiago de Compostela, Santiago de Compostela, Spain
17Department of Physics Aligarh Muslim University, Aligarh, India
18Department of Physics and Technology, University of Bergen, Bergen, Norway 19Department of Physics, Ohio State University, Columbus, Ohio, United States 20Department of Physics, Sejong University, Seoul, South Korea
21Department of Physics, University of Oslo, Oslo, Norway 22Dipartimento di Fisica dell’Universit`a and Sezione INFN, Turin, Italy 23Dipartimento di Fisica dell’Universit`a and Sezione INFN, Cagliari, Italy 24Dipartimento di Fisica dell’Universit`a and Sezione INFN, Trieste, Italy
25Dipartimento di Fisica dell’Universit`a ‘La Sapienza’ and Sezione INFN, Rome, Italy 26Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Catania, Italy 27Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Bologna, Italy 28Dipartimento di Fisica e Astronomia dell’Universit`a and Sezione INFN, Padova, Italy
29Dipartimento di Fisica ‘E.R. Caianiello’ dell’Universit`a and Gruppo Collegato INFN, Salerno, Italy 30Dipartimento di Scienze e Innovazione Tecnologica dell’Universit`a del Piemonte Orientale and Gruppo
Collegato INFN, Alessandria, Italy
31Dipartimento Interateneo di Fisica ‘M. Merlin’ and Sezione INFN, Bari, Italy 32Division of Experimental High Energy Physics, University of Lund, Lund, Sweden
33European Organization for Nuclear Research (CERN), Geneva, Switzerland
34Fachhochschule K¨oln, K¨oln, Germany
35Faculty of Engineering, Bergen University College, Bergen, Norway
36Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia 37Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague,
Czech Republic
38Faculty of Science, P.J. ˇSaf´arik University, Koˇsice, Slovakia
39Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany
40Gangneung-Wonju National University, Gangneung, South Korea
41Gauhati University, Department of Physics, Guwahati, India
42Helsinki Institute of Physics (HIP) and University of Jyv¨askyl¨a, Jyv¨askyl¨a, Finland 43Hiroshima University, Hiroshima, Japan
44Indian Institute of Technology Bombay (IIT), Mumbai, India 45Indian Institute of Technology Indore, Indore, India (IITI)
46Institut de Physique Nucl´eaire d’Orsay (IPNO), Universit´e Paris-Sud, CNRS-IN2P3, Orsay, France 47Institute for High Energy Physics, Protvino, Russia
48Institute for Nuclear Research, Academy of Sciences, Moscow, Russia
49Nikhef, National Institute for Subatomic Physics and Institute for Subatomic Physics of Utrecht University, Utrecht, Netherlands
50Institute for Theoretical and Experimental Physics, Moscow, Russia
51Institute of Experimental Physics, Slovak Academy of Sciences, Koˇsice, Slovakia 52Institute of Physics, Bhubaneswar, India
54Institute of Space Sciences (ISS), Bucharest, Romania
55Institut f¨ur Informatik, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany 56Institut f¨ur Kernphysik, Johann Wolfgang Goethe-Universit¨at Frankfurt, Frankfurt, Germany 57Institut f¨ur Kernphysik, Technische Universit¨at Darmstadt, Darmstadt, Germany
58Institut f¨ur Kernphysik, Westf¨alische Wilhelms-Universit¨at M¨unster, M¨unster, Germany 59Instituto de Ciencias Nucleares, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico 60Instituto de F´ısica, Universidad Nacional Aut´onoma de M´exico, Mexico City, Mexico
61Institut Pluridisciplinaire Hubert Curien (IPHC), Universit´e de Strasbourg, CNRS-IN2P3, Strasbourg, France
62Joint Institute for Nuclear Research (JINR), Dubna, Russia
63Kirchhoff-Institut f¨ur Physik, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany 64Korea Institute of Science and Technology Information, Daejeon, South Korea
65KTO Karatay University, Konya, Turkey
66Laboratoire de Physique Corpusculaire (LPC), Clermont Universit´e, Universit´e Blaise Pascal, CNRS–IN2P3, Clermont-Ferrand, France
67Laboratoire de Physique Subatomique et de Cosmologie (LPSC), Universit´e Joseph Fourier, CNRS-IN2P3, Institut Polytechnique de Grenoble, Grenoble, France
68Laboratori Nazionali di Frascati, INFN, Frascati, Italy 69Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy
70Lawrence Berkeley National Laboratory, Berkeley, California, United States 71Lawrence Livermore National Laboratory, Livermore, California, United States 72Moscow Engineering Physics Institute, Moscow, Russia
73National Centre for Nuclear Studies, Warsaw, Poland
74National Institute for Physics and Nuclear Engineering, Bucharest, Romania 75National Institute of Science Education and Research, Bhubaneswar, India 76Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark 77Nikhef, National Institute for Subatomic Physics, Amsterdam, Netherlands
78Nuclear Physics Institute, Academy of Sciences of the Czech Republic, ˇReˇz u Prahy, Czech Republic 79Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
80Petersburg Nuclear Physics Institute, Gatchina, Russia
81Physics Department, Creighton University, Omaha, Nebraska, United States 82Physics Department, Panjab University, Chandigarh, India
83Physics Department, University of Athens, Athens, Greece
84Physics Department, University of Cape Town and iThemba LABS, National Research Foundation,
Somerset West, South Africa
85Physics Department, University of Jammu, Jammu, India 86Physics Department, University of Rajasthan, Jaipur, India
87Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany 88Politecnico di Torino, Turin, Italy
89Purdue University, West Lafayette, Indiana, United States 90Pusan National University, Pusan, South Korea
91Research Division and ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum f¨ur Schwerionenforschung, Darmstadt, Germany
92Rudjer Boˇskovi´c Institute, Zagreb, Croatia
93Russian Federal Nuclear Center (VNIIEF), Sarov, Russia 94Russian Research Centre Kurchatov Institute, Moscow, Russia 95Saha Institute of Nuclear Physics, Kolkata, India
96School of Physics and Astronomy, University of Birmingham, Birmingham, United Kingdom
97Secci´on F´ısica, Departamento de Ciencias, Pontificia Universidad Cat´olica del Per´u, Lima, Peru 98Sezione INFN, Bologna, Italy
99Sezione INFN, Padova, Italy
100Sezione INFN, Rome, Italy
101Sezione INFN, Cagliari, Italy 102Sezione INFN, Turin, Italy 103Sezione INFN, Trieste, Italy 104Sezione INFN, Bari, Italy
105Sezione INFN, Catania, Italy
106Nuclear Physics Group, STFC Daresbury Laboratory, Daresbury, United Kingdom
107STFC Rutherford Appleton Laboratory, Chilton, United Kingdom
108SUBATECH, Ecole des Mines de Nantes, Universit´e de Nantes, CNRS-IN2P3, Nantes, France
109Suranaree University of Technology, Nakhon Ratchasima, Thailand 110Technical University of Split FESB, Split, Croatia
111Technische Universit¨at M¨unchen, Munich, Germany
112The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland 113The University of Texas at Austin, Physics Department, Austin, TX, United States
114Universidad Aut´onoma de Sinaloa, Culiac´an, Mexico 115Universidade de S˜ao Paulo (USP), S˜ao Paulo, Brazil
116Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil
117Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeurbanne, France 118University of Houston, Houston, Texas, United States
119University of Technology and Austrian Academy of Sciences, Vienna, Austria 120University of Tennessee, Knoxville, Tennessee, United States
121University of Tokyo, Tokyo, Japan 122University of Tsukuba, Tsukuba, Japan
123Eberhard Karls Universit¨at T¨ubingen, T¨ubingen, Germany 124Variable Energy Cyclotron Centre, Kolkata, India
125V. Fock Institute for Physics, St. Petersburg State University, St. Petersburg, Russia
126Warsaw University of Technology, Warsaw, Poland
127Wayne State University, Detroit, Michigan, United States
128Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, Hungary 129Yale University, New Haven, Connecticut, United States
130Yildiz Technical University, Istanbul, Turkey 131Yonsei University, Seoul, South Korea
132Zentrum f¨ur Technologietransfer und Telekommunikation (ZTT), Fachhochschule Worms, Worms,
Contents
0.1 The ALICE Collaboration . . . iii
1 Introduction 1 1.1 Study of Quark–Gluon Plasma . . . 1
1.2 Proposed Physics Programme . . . 2
1.2.1 Heavy-Flavour Production . . . 3
1.2.2 Production of Quarkonia . . . 4
1.2.3 Low-Mass Dileptons . . . 5
1.2.4 Jet Measurements . . . 6
1.2.5 Heavy Nuclear States . . . 7
1.2.6 Comparison of Physics Reach . . . 7
1.2.7 Comparison with Other LHC Experiments . . . 7
1.3 ALICE Detector Upgrade . . . 9
1.4 Running scenario . . . 10
2 Physics Motivation 13 2.1 Heavy Flavour . . . 13
2.1.1 Heavy-flavour Thermalization, Coalescence, and Possible Thermal Production . . . 14
2.1.2 Heavy-flavour Energy Loss . . . 32
2.1.3 Proton–Proton Running Requirements for Heavy-flavour Reference Data . . . 35
2.2 Quarkonia . . . 38
2.2.1 Motivation . . . 38
2.2.2 Inputs for Simulations . . . 42
2.2.3 J/y Yield and the Nuclear Modification Factor . . . 43
2.2.4 J/y Elliptic Flow . . . 43
2.2.5 J/y Polarization . . . 44
2.2.6 Electromagnetic J/y Production . . . 46
2.2.7 y(2S) Measurement . . . 47
2.3.1 Scientific Objectives . . . 48
2.3.2 Experimental Challenges . . . 52
2.3.3 Physics Performance . . . 52
2.4 Jets . . . 60
2.4.1 Jet Measurements in ALICE . . . 63
2.4.2 Jet Structure Modifications . . . 65
2.4.3 Photon–Jet Measurements . . . 67
2.4.4 Heavy Flavour Jets . . . 70
2.4.5 Reference Data . . . 71
2.5 Heavy Nuclear States . . . 72
3 Detectors and Readout Electronics 75 3.1 Introduction . . . 75
3.2 Beampipe . . . 76
3.3 ITS Upgrade . . . 76
3.3.1 Current ITS Performance and Limitations . . . 77
3.3.2 ITS Upgrade . . . 79
3.3.3 Technical Implementation . . . 83
3.4 TPC Upgrade . . . 84
3.4.1 Status and Limitations of the Present TPC . . . 84
3.4.2 Upgrade Concept . . . 85
3.4.3 Expected Performance of the Upgraded TPC . . . 85
3.4.4 Technical Implementation . . . 89
3.4.5 R&D . . . 90
3.4.6 Prototype Test . . . 91
3.4.7 Front-End and Readout Electronics . . . 91
3.5 Upgrade of TOF Readout Electronics . . . 92
3.6 Upgrade of TRD Readout Electronics . . . 93
3.7 Muon Spectrometer Upgrade . . . 95
3.7.1 Muon Trigger Upgrade . . . 95
3.7.2 Muon Tracking Upgrade . . . 96
3.8 Other Upgrade Items . . . 98
4 Data Collection and Processing 101 4.1 Introduction . . . 101
4.2 Requirements . . . 101
4.2.2 Online Data Reduction . . . 102
4.2.3 Online Data Processing Requirements . . . 103
4.2.4 Offline Data Processing and Storage Requirements . . . 104
4.3 Architecture . . . 105
4.3.1 Fast Trigger Processor . . . 105
4.3.2 Dataflow . . . 105
4.3.3 Farm Layout . . . 107
4.3.4 Platform Independence . . . 108
4.3.5 Detector Control System . . . 108
4.3.6 Infrastructure . . . 108
4.4 Research, Prototyping and Development . . . 109
4.4.1 DDL and RORC . . . 109
4.4.2 High-Level Programming of FPGAs . . . 110
4.4.3 FLP and EPN . . . 110
4.4.4 Farm Network . . . 111
4.4.5 Reconstruction Software . . . 113
4.4.6 Parallel HLT Reconstruction on GPU and CPU . . . 117
4.4.7 Analysis of Current AliRoot Performance . . . 118
4.4.8 Plans for the Development of Parallel AliRoot . . . 119
5 Schedule, Cost Estimate and Organization 121 5.1 Schedule . . . 121
5.2 Cost Estimate . . . 125
5.3 Organization . . . 128
Chapter 1
Introduction
Quantum ChromoDynamics (QCD) is well-established as the gauge theory of strong interactions. However, several of its fundamental aspects are not well-understood at present. There remain important open questions about the parton–hadron transition and the nature of confinement, and about the nature of QCD matter at high temperature. A much deeper insight into the mechanisms underlying chiral-symmetry breaking and the origin of light-quark mass is necessary.
This Letter of Intent (LoI) presents the plans of the ALICE (A Large Ion Collider Experiment [1]) collaboration to extend its physics programme, in order to fully exploit the scientific potential of the Large Hadron Collider (LHC) for fundamental studies of QCD, with the main emphasis on heavy-ion collisions. The proposed enhancement of the ALICE detector performance will enable detailed and quantitative characterization of the high density, high temperature phase of strongly interacting matter, together with the exploration of new phenomena in QCD. In the following we outline the physics motivation for running the LHC with heavy ions at high luminosities and summarize the performance gains expected with the upgraded ALICE detector. With the proposed timeline of initiating high-rate operation after the 2018 Long Shutdown (LS2), the objectives of our upgrade plans will be achieved by collecting data into the mid-2020’s.
1.1 Study of Quark–Gluon Plasma
Strongly-interacting matter at very high temperature and density is expected to exist in a state called the Quark– Gluon Plasma (QGP), in which quark and gluon degrees of freedom are liberated, and with properties very different from the hadronic matter we ordinarily find around us. Such conditions of high temperature and density prevailed in the early Universe, a few microseconds after its formation. However, the cosmological QGP epoch is effectively shielded from astronomical observations by the subsequent evolution of the Universe, and the only means to study this fundamental state of matter is via the collision of heavy nuclei in the laboratory. In heavy-ion collisions at ultra-relativistic energies, nuclear matter is heated and brought to values of temperature and density well beyond those required for the creation of QGP, and the same kind of medium that filled the very early Universe is generated for a fleeting instant.
To reach the QGP state, matter has to undergo a QCD phase transition, and that reflects breaking of a fundamental symmetry in the theory. Below the corresponding critical temperature, matter is best described in terms of hadronic degrees of freedom, with quarks and gluons confined in colour-neutral objects. As the temperature rises the hadrons melt (deconfinement phase transition) and quarks and gluons are no longer bound into hadrons. The deconfinement phase transition is caused by the breaking of the Z3-symmetry (exact symmetry in the limit of pure-gauge QCD) at high temperature, and is illustrated in Figure 2.46 (left) by a marked change of the corresponding order parameter, the expectation value of Polyakov loop.
A second phase transition is connected with the generation of hadronic mass, as a consequence of the presence of a quark–antiquark condensate in the vacuum at low temperature. At high temperatures, the vacuum condensate decreases, and the masses of quarks drop to their bare values during the chiral phase transition. This can be seen in Figure 2.46 (right): the expectation value for the density of vacuum quark–antiquark condensate, i.e. the order parameter of the chiral transition, exhibits a sudden drop in the vicinity of the critical temperature. The underlying
reason for this phase transition is the restoration of the approximate chiral symmetry (exact symmetry in the limit of zero bare quark masses) of the QCD Lagrangian.
Lattice-QCD calculations predict that the transition between the QGP and hadronic matter at zero baryo-chemical potential is not a sharp phase transition, but rather a smooth cross-over occurring over a wide temperature range (see Figure 2.46). Recent calculations also suggest that the two phase transitions may occur at different critical temperatures [2]. Lattice QCD further predicts that even at several times the transition temperature, the energy density is still about 15 % below that expected for the Stefan–Boltzmann law for an ideal gas of non-interacting quarks and gluons, with very slow convergence to this limit. This indicates that the effective degrees of freedom in a QGP at finite temperature are not bare quarks and gluons, but rather more complex formations whose nature has not yet been understood. The crucial question of effective degrees of freedom in the QGP is also addressed experimentally, and is an area of intense activity in the field at present. However, it remains a profound challenge for experiment and theory, and may have a deep connection to other areas of physics and cosmology.
The experimental demonstration of these phase transitions, the verification of the lattice QCD predictions reflecting the fundamental symmetries of the theory, and a detailed investigation of the properties of strongly interacting matter at high temperature, are the principal aims of the ALICE scientific programme. Precise determination of the QGP properties, including critical temperature, degrees of freedom, speed of sound, and, in general, transport coefficients and equation of state, is the ultimate goal in the field. This would go a long way towards a better understanding of QCD as a genuine multi-particle theory, shedding light on the complex issues of deconfinement and chiral-symmetry restoration.
The theoretical expectation for many years was that the QGP at high temperature is a weakly-interacting gas of quarks and gluons, with the constituents traveling long distances between interactions, relative to the size of a proton. Heavy-ion experiments indicate instead fundamentally different and surprising behaviour of the created matter: the formation of a strongly-coupled plasma with very short mean free path, which exhibits a high degree of collectivity and flows, and which absorbs a significant fraction of high-energy partons propagating through it. Over time, the image of the QGP as an almost-perfect, inviscid liquid emerged from the experimental investigation at both, CERN SPS and BNL RHIC. With the first two years of LHC running, the ALICE collaboration has confirmed this basic picture, observing the creation of hot hadronic matter at unprecedented values of temperatures, densities and volumes. The first results extended the precision and kinematic reach of all significant probes of the QGP that had been measured over the past decade, and new and intriguing phenomena were observed with charm mesons and charmonia.
The observation that the QGP is a near-perfect liquid is based on measurements of inclusive spectra (radial flow) and azimuthal anisotropy of particle production (elliptic flow) for identified hadrons at soft transverse momenta (pT), up to about 3 GeV/c. This is further confirmed by comparison to model calculations based on viscous rela-tivistic hydrodynamics. Hydrodynamics is a general approach to fluid dynamics, describing the long-wavelength behaviour of a complex system in quasi-equilibrium, and serves as a powerful tool to determine the QGP prop-erties. The good agreement of hydrodynamic calculation with ALICE and other experiments flow measurements provides strong evidence for the formation of a quasi-equilibrated QGP in heavy-ion collisions at LHC energies. The very low ratio of shear-viscosity to entropy-density of the QGP, inferred from the comparison of model calcu-lations and experimental measurements, demonstrates very short mean free path inside this medium composed of strongly-coupled quasi-particle modes, whose origin is the subject of further experimental study.
1.2 Proposed Physics Programme
The LHC provides the optimal experimental conditions to study the QGP, due to the following:
– the net baryon density in the central (mid-rapidity) region is very small, corresponding to the conditions of the early Universe;
– the initial temperature and energy density are the highest achievable in the laboratory; – the large collision energy ensures an abundance of perturbatively calculable hard QCD processes. The study of the strongly-interacting state of matter in the second generation of LHC heavy-ion studies following LS2 will focus on rare probes, and the study of their coupling with the medium and hadronization processes. These include heavy-flavour particles, quarkonium states, real and virtual photons, jets and their correlations with other
probes. The cross sections of all these processes are significantly larger at LHC than at previous accelerators. In addition, the interaction with the medium of heavy-flavour probes is better controlled theoretically than the propagation of light partons. All these investigations should involve soft momentum scales, and thus benefit from the ALICE detector strengths: excellent tracking performance in high-multiplicity environment and particle identification over a large momentum range. In most of these studies, the azimuthal anisotropy of different probes will be measured. Major highlights of the proposed programme focus on the following physics questions:
– Study of the thermalization of partons in the QGP, with focus on the massive charm and beauty quarks. Heavy-quark azimuthal-flow anisotropy is especially sensitive to the partonic equation of state. Ultimately, heavy quarks might fully equilibrate and become part of the strongly-coupled medium.
– Study of the low-momentum quarkonium dissociation and, possibly, regeneration pattern, as a probe of deconfinement, and an evaluation of the medium temperature.
– Study of the production of thermal photons and low-mass dileptons emitted by the QGP. This should allow to assess the initial temperature and the equation of state of the medium, as well as to shed light on the chiral nature of the phase transition.
– Study of the in-medium parton energy-loss mechanism that provides both a testing ground for the multi-particle aspects of QCD and a probe of the QGP density. The relevant observables are: jet structure, jet–jet and photon–jet correlations, and jet correlations with high-momentum identified hadrons and heavy-flavour particle production in jets. In particular, it is crucial to characterize the dependencies of energy loss on the parton colour-charge, mass, and energy, as well as on the density of the medium.
– Search for heavy nuclear states such as light multi-L hyper-nuclei 5
LLH, bound states of (LL) or the H
dibaryon, (Ln) bound state, as well as bound states involving multi-strange baryons; a systematic study of light nuclei and anti-nuclei production.
Below we outline the basic physics motivation for these measurements; the details and the corresponding perfor-mance studies are described in Chapter 2.
1.2.1 Heavy-Flavour Production
High-precision measurements of charm and beauty production in heavy-ion collisions at the LHC is one of the principal physics motivations for the upgrade of the ALICE detector and the high-luminosity running of the exper-iment. The envisaged measurements of open heavy-flavour production will make possible to precisely determine important parameters of the strongly interacting matter that are not accessible with the present experimental setup, see Section 2.1 for details. Two topics that need high-precision and high-statistics measurements are proposed to study:
– thermalization of heavy quarks in the medium, by determination of the baryon-to-meson ratio for charm and for beauty particles, the azimuthal-flow anisotropy for charm mesons and baryons and beauty particles, and the possible in-medium thermal production of charm quarks;
– parton mass and colour-charge dependence of in-medium energy loss, by measuring the pT-dependencies of the nuclear modification factors separately for D and B mesons, and comparing them with those for light-flavour particles.
These two topics are closely connected: the in-medium heavy-quark energy loss lowers the momenta of heavy quarks, they may thermalize in the system, and thus participate in the collective flow dynamics. The simulta-neous observation of the two phenomena opens the possibility for determination of the heavy-flavour transport coefficients. Heavy-flavour production plays a special role in heavy-ion physics: it provides a calibrated probe (input pTspectra calculable from perturbative QCD), and, in addition, this probe is well-tagged (identified), from production till observation, which enables a unique access to its interactions in the QGP, also in the low- and intermediate-pTregime.
The ALICE collaboration already presented the first results on D-meson production in heavy-ion collisions. To address the physics questions mentioned above, these measurements have to be extended to a lower pT, include charm baryons (possibly also charm–strange baryons) and beauty particles. The capability of studying yields and spectra of particles containing heavy quarks is given by the performance of secondary-vertex isolation close to
the primary-interaction vertex. Charm production is measured by the reconstruction of exclusive hadronic decays using topological selection of a secondary vertex. Particle identification for charged hadrons is needed to reduce the very large backgrounds in heavy-ion collisions, especially at low transverse momentum. In addition, charm and beauty can be tagged in semi-leptonic decays, detecting electrons and muons. Therefore, the excellent particle-identification capabilities of the ALICE detector have to be preserved. However, important physics topics, such as the study of heavy-flavour baryons or of open heavy-flavour hadrons with more than one heavy quark, are beyond the capability of the present detector.
Preliminary measurements of the elliptic-flow coefficient v2(the amplitude of second order harmonic of the az-imuthal distribution) for different D mesons in 30–50 % central Pb-Pb collisions were obtained by the ALICE experiment; the result is very intriguing, because it suggests that D mesons in the pTrange 2–6 GeV/c may indeed take part in the collective flow. Models taking into account heavy-quark transport in the medium, with various implementations of the quark–medium interaction, predict a large v2for D mesons at low transverse momenta that should become accessible with the upgraded ALICE detector. The low-pTB mesons v2, not in the reach of present experiments, is predicted to be substantially smaller than that for D mesons. Such difference in the az-imuthal anisotropy at intermediate pTis inherent to the QCD interaction mechanisms, and would thus serve as an important test of our understanding of the nature of matter formed in heavy-ion collisions.
The study of heavy-flavour energy loss has a particular interest, because gluon radiation from heavy quarks at small angles is predicted to be suppressed, in comparison to the case of light partons. Moreover, at LHC energies, high-pTlight-flavour hadrons are dominantly produced in gluon fragmentation, and gluons presumably lose more energy than quarks, due to their larger colour charge. Consequently, the clear prediction for the hierarchy of energy loss in strongly interacting matter is: gluons lose more energy than charm quarks, and the latter lose more energy than beauty quarks. Experimentally, this should be investigated by comparing the nuclear modification factors as a function of pTof light-flavour hadrons, of charm particles, and that of beauty particles. The first measurement
of the D-meson nuclear modification factor for pTabove 2 GeV/c has been already published by the ALICE
collaboration. In order to access pTdown to zero, the improvement in vertexing capabilities is mandatory. This is even more true for a precision measurement of the B-meson nuclear modification factor, where, in addition, a substantial increase in event statistics is necessary.
1.2.2 Production of Quarkonia
Charmonium is the first hadron for which a clear mechanism of suppression in QGP was proposed, based on the colour-charge analogue of Debye screening. Because of difficulties to explain the observed suppression pattern, especially they(2S) production, alternative models were proposed. The statistical hadronization model was moti-vated by the observation that they(2S)-to-J/y production ratio has the value corresponding to that obtained at the chemical freeze-out temperature determined for other hadrons. In this model, the charm quarks produced in the initial hard collisions thermalize in the QGP and are distributed into hadrons at chemical freeze-out. Charmonium states are produced, together with all other hadrons, only at chemical freeze-out. The predictions of this model depend on the amount of available charm quarks, i.e. on the charm-production cross section, which we aim to measure with high precision.
Another model proposes kinetic recombination of c and ¯c quarks in the QGP as an alternative charmonium pro-duction mechanism. In this model a continuous dissociation and regeneration of charmonium takes place in the QGP over its entire lifetime. Besides the charm-production cross section, the input parameters of this model are the time dependence of the temperature, as well as other relevant cross sections and assumptions on the melting scenarios of charmonium states. Important observables, like the production yields and elliptic flow as a function of pTand rapidity, are calculated within this kinetic transport model.
The measurement of the production of different charmonium states in Pb-Pb collisions at the LHC should pro-vide a definitive answer on the question of J/y production mechanism in the QGP. Details on the expected per-formance are given in Section 2.2. A clear pT-dependent pattern of J/y suppression, seen in the first ALICE measurements and being in good agreement with the hight-pTCMS results, strongly suggests that a (re)generation mechanism plays a significant role in low-pT( 3 GeV/c) J/y production at LHC energies. Indeed, both the statis-tical hadronization and kinetic transport model predictions do explain these first observations. Concerningy(2S) production, preliminary results presented by the ALICE and CMS collaborations show some tensions, but are in-conclusive due to the large uncertainties. However, already the first charmonium results from the LHC indicates the importance of the measurement down to zero pTfor the understanding of underlying production mechanism. In addition, large rapidity coverage of the ALICE measurements (and complementary to that of CMS) will impose
further constraints to relevant models. Statistically significant measurements of different charmonium states is also mandatory, andy(2S) is the prime example calling for high statistics. A possibility of cc-production measurement in heavy-ion collisions with the upgraded ALICE detector is under investigation.
The J/y produced by the recombination of c ¯c pairs in later stages of the collisions would inherit the elliptic flow of the charm quarks in the QGP. In this respect, like for the open heavy-flavour particles, the measurement of quarko-nium elliptic flow is especially promising to complement the measurements of yields and nuclear modification factors. ALICE recently reported the first measurement of J/y v2in the pTrange 0 < pT<10 GeV/c at forward rapidities in Pb–Pb collisions, and a hint for non-zero elliptic flow was observed. With the upgraded detector, such a measurement will be possible on a qualitatively new precision level. Other measurements that will benefit from the ALICE upgrade are J/y polarization and J/y production in very low pT(< 300 MeV/c), where an excess, which may be attributed to J/y photo-production, is observed.
Given the very large energy of the collisions at LHC, an abundant production of charm and beauty quark–antiquark pairs is expected in the initial hard-scattering processes (about 80 and 3, respectively, per central Pb-Pb collision). The LHC has opened up the measurement of the° family in Pb-Pb collisions, where a suppression of the excited states has been observed by CMS. Still, the density of charm quarks is more than one order of magnitude larger than that of beauty, and therefore the behaviour of charmonium is expected to be completely different from that of ° states. A detailed study of the ° states will be performed by the ATLAS and CMS collaborations, ALICE will complement these measurements, especially in the forward rapidity region.
1.2.3 Low-Mass Dileptons
Electromagnetic radiation is produced during all stages of the heavy-ion collision, and, being detected either as a real photon or as a dilepton pair, it brings information about the entire system evolution, since the detected particles do not interact strongly with the medium. The measurement of low-mass dilepton production gives an insight into the bulk properties and the space–time evolution of the hot and dense QCD matter formed in ultra-relativistic heavy-ion collisions, and provides an access to the hadronic excitation spectrum in the medium. Comprehensive measurements of low-mass dileptons in heavy-ion collisions at the LHC, described in Section 2.3, will allow to study the following topics:
– The masses of the light-quark particles are connected with spontaneous breaking of chiral symmetry of QCD. The theory predicts that this fundamental symmetry is restored at high temperature, leading to sub-stantial distortions of the vector and axial-vector spectral functions. Such modifications, in particular for ther meson, should be observable in dilepton spectra.
– The temperature reached by the system can be assessed by measuring the dilepton invariant-mass and pTspectra. The study of low-mass dileptons also allows an estimate of real direct-photon production which is complementary to direct real-photon measurements.
– The lifetime of the system and its overall space–time evolution can be inferred from low-mass dilepton measurements. The possibility to disentangle early and late contributions makes the evolution of collectivity and the fundamental properties related to it, such as transport coefficients, viscosity, and the equation of state potentially accessible.
The dilepton invariant-mass spectrum contains information about the relevant degrees of freedom of the system and their dependence on temperature and density. At masses below 1 GeV/c2the spectrum is dominated by the contribution of the light vector resonances, in particular of ther meson. As a consequence of the strong coupling between ther resonance and the hot and dense hadronic matter, close to the phase-transition boundary the r-meson spectral function strongly broadens. This behaviour, predicted by multi-particle QCD theory, was experimentally demonstrated in heavy-ion collisions at CERN SPS.
Recent lattice QCD calculations indicate that the critical temperature of the deconfinement phase transition may be higher than that of the chiral phase transition (see Figure 2.46), in that case the chiral symmetry will remain restored still in a hot hadronic resonance gas. As a consequence of the restoration chiral symmetry the vector and axial-vector spectral functions are modified, utimately leading to a degeneracy of the two. While the latter is not measurable experimentally, the observation of the vector spectral-function modification is essential to reveal chiral-symmetry restoration, using QCD sum rules and constraints from lattice QCD. A precise measurement of the low-mass dilepton spectrum in heavy-ion collisions constitutes the only known means to assess experimentally the nature of the chiral phase transition.
The spectrum of real direct-photons can be inferred by the extrapolation of measurements of very low-mass dilep-tons to zero mass; this method is complementary to that using direct measurement and is sufficiently accurate for pTabove 1 GeV/c (when measuring dilepton masses down to about 200 MeV/c2). The virtual-photon mea-surement has the advantage of much less physical background than the direct-photon meamea-surement, although the yield of virtual photons is suppressed compared to real ones. This extrapolation gives access to the direct-photon spectrum in the pTregion (1–5 GeV/c) where the thermal contribution is expected to dominate. The temperature at early stage of the system is accessible by dilepton invariant-mass spectrum at larger masses (1.5–2.5 GeV/c2). The equation of state, i.e. the relation between the pressure and the temperature, is one of the most fundamental characteristics of strongly interacting matter. It determines the expansion history of the early Universe and has obvious consequences for the space–time evolution of the matter formed in heavy-ion collisions. The equation of state is a basic input to hydrodynamical models which give a good description of the observed collective flow. Dilepton pairs are emitted at all stages of the collision, causing a complex collectivity pattern when studied as a function of the invariant mass and pT. In heavy-ion collisions at the LHC, significantly higher initial temperatures are reached than at previous accelerators, entailing even more pronounced contributions from the QGP to dilepton production at high masses. A systematic and detailed investigation of radial and elliptic flow as a function of the invariant mass and pTwill give access to the evolution of collectivity at different stages of the collision, and will provide a unique experimental handle on the equation of state of partonic matter.
We aim to measure low-mass dileptons with the upgraded ALICE detector exploiting the e+e channel. The
measurement of e+e pairs in Pb–Pb collisions at LHC energies is experimentally very challenging. The require-ment for the acceptance is to reach dilepton invariant masses and transverse morequire-menta values as low as the critical temperature, i.e. Tc' 150 MeV. This implies electron detection down to pTin the range 0.1–0.2 GeV/c. To in-crease the acceptance for low-pTelectrons in this measurement, we plan to decrease the field of the main ALICE solenoidal magnet to 0.2 T (from the nominal value 0.5 T), this means that a special Pb–Pb run will be necessary with such settings. The main challenge in this measurement and analysis is the rejection of different backgrounds, such as electrons from Dalitz decays, charm decays and from photon conversions in detector material. To achieve this goal, we will rely on: improved tracking at very low momenta, enhanced vertexing capabilities suppressing the photon-conversion and charm-decay backgrounds, and low material-budget tracker reducing the conversion prob-ability. Additional gain comes from an increased statistics due to the high-rate capability of the upgraded ALICE detector. This will be a unique measurement in the highest-energy heavy-ion collisions, giving access to the initial temperature, the partonic equation of state, and nature of chiral phase transition at vanishing baryon density.
1.2.4 Jet Measurements
The main motivation for measuring jets in heavy-ion collision is to map out the energy loss of hard scattered partons in the QGP, and thereby access the properties of the strongly interacting medium. On their way out of the medium, partons interact with the QGP, losing energy through both radiative and elastic channels with a magnitude of the energy loss strongly dependent on the density of colour charges in the medium. The observed energy loss is usually referred to as jet quenching. In effect, the energy loss softens the fragmentation function of the jet,
resulting in an enhancement of low-momentum hadron multiplicity and a suppression of high-pThadrons. A
precise measurement of jet-quenching effects has the potential to probe the medium at the hottest, densest stage of the collision. Specific to ALICE, following studies, discussed in Section 2.4, will benefit from the upgrade programme:
– ALICE will measure particle-identified fragmentation functions and their in-medium modifications over a wide momentum range, exploiting its particle identification systems. Such a study, unique to ALICE, will shed light on the thermalization of fast quarks and gluons, as well as on the response of the medium to large local energy deposits by partons.
– Heavy-flavour production in jets, especially at low z (fraction of original parton momentum) is another domain where ALICE will bring a unique contribution to jet studies, with its excellent performance for heavy-flavour particle detection at low pT.
– In photon–jet correlations, the precise measurement of photons, will calibrate the energy of the partons recoiling against them, opening the possibility of detailed jet investigations down to relatively low transverse energies (ET⇡ 20 GeV). Moreover, a photon-tagged jet, is predominantly a quark jet, unlike for the unbiased jet sample, which is dominated by gluon jets; this provides another way to study the energy-loss hierarchy mentioned above.
– Excellent low-momentum tracking will help ALICE to investigate the fate of the energy quenched in the medium, which in the current measurements is usually hard to distinguish inside the underlying event and its fluctuations.
Precise measurements of the jet structure and of its modification in terms of energy flow, of the modification of jet-energy patterns, and of the broadening of jets due to interactions in matter promises to offer new, fundamental insights into the underlying theory. The ALICE strength is that it provides tools for differential studies of the jet structure in two approaches: track reconstruction and separation down to low momentum; and particle identifi-cation including heavy-flavour. The benefits of the high-rate upgrade will be also substantial for the photon–jet correlations studies, which are usually limited by the small cross section of electromagnetic processes and the challenging extraction of isolated photons in heavy-ion collisions.
1.2.5 Heavy Nuclear States
Another area where the ALICE measurements are unique is the search for exotic objects produced in heavy-ion collisions. The ALICE detector has superior particle identification capability combining the measurements of different detectors and using various techniques. For example, ALICE already reported the successful search for4He antinuclei. With the high-rate upgrade, the inspection of as many as 1010Pb–Pb events should become feasible; this will allow a systematic study of the production of nuclei and antinuclei and bring within reach the detection of light multi- hyper-nuclei, such as 5
LLH.
Other exotic objects to search for include bound states of (LL) or the H dibaryon, a possible (Ln) bound state, as well as bound states involving multi-strange baryons. The important issue to note here is that, using the ALICE apparatus, in addition to search for the existence of these states, we can also study their decay properties. The presence of strangeness in these objects, making them more flavour symmetric than ordinary matter, may increase their stability. Such observations would give access to completely new information on hyper-nuclei and other heavy-nuclear bound states. The production rate estimates for different states are given in Section 2.5.
1.2.6 Comparison of Physics Reach
The improvement in the physics reach for different observables is summarized in Table 1.1. The comparison is presented between two scenarios (see also Section 1.3):
– the approved ALICE programme, which corresponds to delivered integrated luminosity of 1 nb1, however, for observables relying on minimum-bias data (such as heavy-flavour production and low-pTdielectrons) only 1/10 of this is usable due to the TPC rate limitation;
– the proposed ALICE upgrade with assumed integrated luminosity of 10 nb 1, fully used for
minimum-bias data collection, and a special low-magnetic-field run with 3 nb 1of integrated luminosity for low-pTdielectron study.
Table 1.1 illustrates that, with the ALICE upgrade, in some cases (D meson from B decays RAA, D meson elliptic flow) we will move from an observation to the precision measurement, and other signals (dielectrons) will become accessible.
1.2.7 Comparison with Other LHC Experiments
The ALICE upgrade and the proposed physics programme build on the demonstrated strengths of the current ALICE detector configuration:
– excellent tracking performance, especially at low momenta (down to pT' 150 MeV/c);
– efficient secondary vertex reconstruction, in particular for heavy-flavour particle decays: the resolution in the distance of closest approach between a track and the interaction vertex in the transverse projection at pT=1 GeV/c issrj1GeV' 60 µm;
– very low material budget of the tracking system, the thickness of the Inner Tracking System is 7–8 % of radiation length for normal-incident particles (i.e. 1.2–1.3 % per tracking layer), the overall thickness including the TPC is ' 10–11 %;
